Experimental Results of the AISC Full-Scale Column Blast Test

66 Pages·2006·5.25 MB·English

TR-06-20.2

Karagozian & Case

2550 North Hollywood Way, Suite 500

Burbank, CA 91505-5026

www.kcse.com
E R
XPERIMENTAL ESULTS OF THE
AISC F -S C B
ULL CALE OLUMN LAST
T
EST

Joseph M. Magallanes
Ruben Martinez
John W. Koenig

March 21, 2006

Prepared for:

The American Institute of Steel Construction
1 East Wacker Drive., Suite 700
Chicago, IL 60601

Contract No. KC-05-27.2

© 2006, Karagozian & Case
TR-06-20.1

E R
XPERIMENTAL ESULTS OF THE
AISC F -S C B
ULL CALE OLUMN LAST
T
EST

Joseph M. Magallanes
Ruben M. Martinez
John W. Koenig

March 21, 2006

Prepared for:

The American Institute of Steel Construction
1 East Wacker Drive., Suite 700
Chicago, IL 60601

Contract No. KC-05-27.2
© 2006, Karagozian & Case
EXECUTIVE SUMMARY
This summary report describes the full-scale blast test of a steel wide-flange column
conducted for the American Institute of Steel Construction (AISC). Karagozian & Case (K&C)
was the prime contractor and was responsible for creating the overall test plan, the design of the
test article, the design of the reaction structure, and field coordination during the assembly and
installation of the test article. The test was conducted by the Energetic Materials Research and
Testing Center (EMRTC), subcontractor to K&C, on 02 March 2006 at the Multi-Bay Test
Facility (MBTF) located within the EMRTC Field Laboratory in Socorro, NM.
The AISC column test investigated the behavior of a W14×233 column of ASTM A992,
Gr. 50 structural steel, subjected to a large explosive, similar to that which can be expected in a
terrorist attack on the exterior of a building with a vehicle bomb. The explosive, consisting of
4,000 pounds TNT-equivalent of Ammonium Nitrate/Fuel Oil (ANFO), was placed at a slant
angle with respect to the column at an effective standoff of 15’-6” from the center of the column.
The complete details of the column test specimen, reaction structure, explosive charge, and test
results are summarized in this report.

i
ACKNOWLEDGEMENTS
Funding for the test was solely provided by AISC, with Mr. Charlie Carter serving as the
project director. Mr. Carter’s support, input, and guidance was extremely valuable to the entire
effort, from planning the design of the test, to the review of the draft report. Substantial
additional support was provided in the form of donation of time, services, and materials from
numerous fabricators and engineers. K&C would specifically like to acknowledge the efforts of
Mr. Tom Schlafly of AISC who coordinated the fabrication of the test article,
Mr. Hans Warkentin from Trevian Projects Ltd. who donated numerous hours during Christmas
of 2005 to generate the shop drawings of the test article, and Mr. Bill Lindley of the W&W Steel
Co. who generously donated and fabricated all steel materials for the test article. Finally, the
input and suggestions of various engineers were extremely valuable to this project. In particular
Dr. Jack Hayes of the National Institute of Science and Technology, Dr. Stanley Woodson of the
Engineering Research and Development Center, Construction Engineering Research Laboratory,
and Mr. David Bonneville and Mr. Robert Pekelnicky of Degenkolb Engineers.
ii
TABLE OF CONTENTS
Section Page

EXECUTIVE SUMMARY........................................................................................... i
ACKNOWLEDGEMENTS........................................................................................... ii
FIGURES....................................................................................................................... iii
TABLES........................................................................................................................ v

1 INTRODUCTION......................................................................................................... 1-1
1.1 SCOPE............................................................................................................... 1-1
1.2 TEST BACKGROUND..................................................................................... 1-1
1.3 TEST OBJECTIVE............................................................................................ 1-2
1.4 ORGANIZATION OF THE REPORT.............................................................. 1-2
2 TEST BED SETUP........................................................................................................ 2-1
2.1 TEST ARTICLE................................................................................................ 2-1
2.2 INSTALLATION TO THE REACTION STRUCTURE.................................. 2-1
2.3 INSTALLATION OF CLADDING.................................................................. 2-2
2.4 CHARGE AND STANDOFF............................................................................ 2-3
2.5 INSTRUMENTATION AND HIGH-SPEED VIDEO...................................... 2-4
2.6 PRETEST PREDICTION...................................................................................2-4
3 TEST RESULTS............................................................................................................ 3-1
3.1 OBSERVED RESULTS.................................................................................... 3-1
3.2 COLUMN RESIDUAL DEFLECTION............................................................ 3-2
4 DISCUSSION OF RESULTS........................................................................................ 4-1
4.1 RESPONSE OF COLUMN............................................................................... 4-1
4.2 STEEL FRACTURE.......................................................................................... 4-2
5 CONCLUSIONS............................................................................................................ 5-1
5.1 CONCLUSIONS................................................................................................ 5-1
5.2 RECOMMENDATIONS................................................................................... 5-1
6 REFERENCES.............................................................................................................. 6-1

Appendix
A TEST SPECIMEN CONSTRUCTION DOCUMENTS.............................................. A-1

iii
FIGURES
Figure Page

1-1 Explosive threat of interest to the FEMA/DHS study.................................................. 1-3
1-2 The FEMA/DHS study focused on the 14WF228 column at gridlines G3
subjected to a 4,000-pound TNT equivalent explosive................................................ 1-4
1-3 Section properties of the 14WF228 column................................................................. 1-5
2-1 The AISC test column specimen................................................................................... 2-6
2-2 Section properties of the W14×233 column................................................................. 2-7
2-3 Photograph of the column base and header assemblies prior to filling with
concrete......................................................................................................................... 2-8
2-4 Reaction wall at the MBTF site at EMRTC.................................................................. 2-9
2-5 Photographs of the installation of the test article to the MBTF reaction wall.............. 2-10
2-6 Photographs of the of the test article during curing of the footing............................... 2-11
2-7 Installation of the brick cladding enclosure around the test column............................ 2-12
2-8 Chronological view of AISC steel column cladding installation.................................. 2-13
2-9 Photograph of the completed test column including the cladding enclosure................ 2-14
2-10 Illustration of the positioning of the explosive to achieve an effective slant
standoff of 15’-6” measured from the center of the column to the center of the
charge............................................................................................................................ 2-15
2-11 Photograph of a similar ANFO explosive setup using a Sonotube............................... 2-16
2-12 Pretest photographs of the charge stand and explosive positioned at an effective
slant standoff of 15’-6” measured from the center of the column to the center of
the charge in the direction normal to the MBTF reaction wall..................................... 2-17
2-13 Estimate of the air blast loadings from 4,000 lb TNT at 15’ standoff.......................... 2-18
2-14 Air blast loadings versus range for an ideal 4,000-pound TNT hemisphere on the
ground surface............................................................................................................... 2-18
2-15 High-speed video camera details.................................................................................. 2-19
3-1 Close-up video stills of the test bed moments after detonation.................................... 3-4
3-2 Video stills of the test bed moments after detonation................................................... 3-6
3-3 Posttest photograph of the crater left by the explosion................................................. 3-8
3-4 Pre and posttest photographs of the column................................................................. 3-9
3-5 Posttest photographs of the column and reaction system............................................. 3-10
3-6 Close-up posttest photograph of the column................................................................ 3-11
iv
FIGURES (CONTINUED)
Figure Page

3-7 Posttest photographs of the base of the column............................................................ 3-13
3-8 Process of conducting the posttest survey of the column to quantify the residual
deflection of the column’s front flange as a function of height along the column....... 3-14
3-9 Residual deflection of the column’s front flange as a function of height along the
column........................................................................................................................... 3-15
4-1 Variations in the response of steel wide-flange columns with and without cladding... 4-3
4-2 Response of the 14WF228 column as computed simplified HFPB FE calculations
for the FEMA/GSA effort that included simplify loading methodologies................... 4-5
4-3 Failure modes of wide-flange sections as observed in a separate test program
funded by AISC............................................................................................................ 4-6

v
TABLES
Table Page

2-1 High-speed video camera information.......................................................................... 2-5
3-1 Residual deflection of the column as measured in a posttest survey............................ 3-3

vi
SECTION 1
INTRODUCTION
1.1 SCOPE
This summary report describes the full-scale blast test of a steel wide-flange column
conducted for, and funded by, the American Institute of Steel Construction (AISC).
Karagozian & Case (K&C) was the prime contractor and was responsible for creating the overall
test plan, the design of the test article, the design of the reaction structure, and field coordination
during the assembly and installation of the test article. The test was conducted by the Energetic
Materials Research and Testing Center (EMRTC), subcontractor to K&C, on 02 March 2006 at
the Multi-Bay Test Facility (MBTF) located within the EMRTC Field Laboratory in
Socorro, NM.
The AISC column test investigated the behavior of a W14x233 column of ASTM A992,
Gr. 50 structural steel, subjected to a large explosive, similar to that which can be expected in a
terrorist attack on the exterior of a building with a vehicle bomb. The explosive, consisting of
4,000 pounds TNT equivalent of Ammonium Nitrate/Fuel Oil (ANFO), was placed at a slant
angle with respect to the column at an effective standoff of 15’-6” from the center of the column.
The complete details of the column test specimen, reaction structure, explosive charge, and test
results are summarized in this report.
1.2 TEST BACKGROUND
The Federal Emergency Management Agency (FEMA) and the Department of Homeland
Security (DHS) have recently joined efforts in conducting a study on steel structures regarding
the blast-resistant benefits gained by implementing current seismic design and detailing
requirements. This effort is similar to a previous study focusing on reinforced concrete buildings
[1]. The current FEMA/DHS effort is being executed with a joint effort between the U.S. Army
Corps of Engineers Engineering Research and Development Center (ERDC), out of Vicksburg,
MS, and Degenkolb Engineers, based out of San Francisco, CA. Numerous experts in various
disciplines encompassing the study, such as steel fracture, blast effects, and seismic design, serve
on a peer review panel for this FEMA/DHS study and include members of AISC and K&C.
The study focused on a modified version of an existing steel structure subjected to an
explosive charge similar to that experienced during the terrorist attack on the Murrah Building in
Oklahoma City in 1995. The scenario of interest to the study is illustrated in Figure 1-1. The
structure consists of a steel-framed gravity system supporting a steel metal deck with concrete
infill and relies on moment-frames as the building’s primary lateral force-resisting system
(LFRS). Since the structure reflects older LFRS detailing requirements, several building retrofits
were considered to upgrade the existing building to conform to current seismic design
requirements for areas of high seismicity (e.g., San Francisco, CA). A blast effects analysis of
each retrofit scheme was executed to quantify the blast resistant benefits obtained through
implementing these various seismic upgrade schemes.
1-1
A threat representative of the attack on the Murrah Building was determined by the
FEMA/DHS peer review panel to be a 4,000-pound TNT-equivalent charge positioned away
from the column at gridline G3 as illustrated in Figure 1-2. This equated to an effective slant
standoff of 15’-6” from the center of this column to the center of the explosive source.
The column at gridline G3 is an older AISC 14WF228 section [2]. As summarized in
Figure 1-3, the column has a section depth of 16 inches with a nominal web thickness of
1.045 inches, and nominal flange width and thickness of 15.865 and 1.688 inches, respectively.
In the FEMA/DHS structure, the column was founded in a concrete pilaster within a 10 inch
thick concrete retaining wall as was shown in Figure 1-2. The column was continuous through
the second floor and framed by three W24× girders on three sides, each having moment
connections to the column. The column also had a 2’-6” square architectural enclosure
composed of 2-inch thick marble cladding. The clear height from the top of the base concrete to
the bottom of the W24× girder is 18’-9”.
The study, near its completion at the time of the delivery of this report, will conclude
important findings that will be available for reference by both the construction and engineering
design communities. However, one source of uncertainty at this moment is the actual behavior
of the first story column at gridline G3. If the column is significantly damaged from the
explosion, the result may be a situation in which large redistribution demands are created on the
exterior perimeter frames in the evaluation of progressive collapse potential. Determining the
behavior of this column is paramount to the conclusions drawn from this FEMA/DHS study.
1.3 TEST OBJECTIVE
Spurred by this FEMA/DHS effort, the American Institute of Steel Construction (AISC)
contracted K&C, with EMRTC as its subcontractor, to execute a blast test of a representative test
article of this steel column. Hence, the primary objective of this test was to experimentally
determine the response of the column subjected to a 4000-pound TNT-equivalent explosion at an
effective slant range of 15’-6”.
1.4 ORGANIZATION OF THE REPORT
This report is divided up into several sections to provide a concise summary of the test
conducted to achieve this objective. Section 2 describes the test bed setup. Included in this
discussion is a detailed summary of the test article, supporting structure, explosive, and the
active instrumentation fielded for the test. Section 3 contains the test results. Here, high-speed
video photography of the test is shown and the response of the column illustrated with posttest
photographs. Section 4 provides a discussion of the test results. Section 5 summarizes the
important conclusions gained from the test and provides recommendations for future research.
1-2